The present invention refers to a method for consolidating stone blocks, or stone materials in general, through sealing them with hardenable resins.
In the activity of transforming natural stone blocks into slabs or hand-manufactured articles the raw material, the block, is often defective and conditions the whole production cycle, from the mining stage to the laying of the hand-manufactured articles.
It is well known that marbles and natural stones in general are not homogeneous materials in that their structure is highly influenced by the mineralogical composition and by the geologic history of mineral deposits.
While other raw materials originate from production processes that can be monitored and improved, marble, granite and other natural stones are the result of millions of years of modifications of the terrestrial crust and testify to this through their structural heterogeneity.
On the other hand very often the heterogeneity of parts confers to a stone its appreciated chromatic and decorative characteristics. More precious and polychrome materials are naturally most defective materials because of their tormented geologic formation.
After the manufacturing process the presence of structural defects in materials complicates yard problems for laying, reduces the lifetime of hand-manufactured articles and causes a more difficult and expensive maintenance.
Extractive activity is the first stage of the production cycle. Quarry operations are conditioned by defects of the raw material, macro-defects, fissures and structural discontinuities of the deposit and are driven by them.
When the care taken is not sufficient to guarantee a percentage of marketable extracted material that covers the extraction costs, the layer is abandoned.
Next working phase comprises cutting of the quarry block by means of a saw frame for square blocks suitable for the production of slabs or by means of diamond disk saws for shapeless blocks or blocks squared but with many structural defects.
From saw frames can be obtained slabs that are sections of the quarry block, from disk saws can be obtained directly small dimension objects.
The structural defects present in the block influence the results in both cases. From the saw frame could come out broken slabs and, in the more serious cases, the whole block could crumble while cutting, with potential damage to the frame and with high economic losses.
From disk saws could instead come out a certain number of broken pieces.
In the following squaring operations of the manufactured articles and their calibration and/or polishing, the fissures and the residual fractures, also if they didn""t cause fractures and divisions while cutting, can still create problems, causing the division of the same articles along the line of fracture.
While products that come out broken from disk saws could not be sheltered and find residual uses in the ulterior reduction of size or in the composition of various products in which the fragments are joined together by means of cement and resinous glues, for reparation by gluing the parts together, with approximate and expensive operations, is often attempted.
The slabs so recomposed and also slabs not broken, but that don""t give sufficient guarantees for going on with the process up to the final polishing, are often subjected to reparation and reinforcement operations.
These operations consist in dripping very fluid gluing resins on the surface of the damaged slab so that their infiltrating and following hardening connects together the disconnected parts.
Often together with this provision is made a reinforcement of the back face of the slab by means of webs or fiber glass or cotton or other fibers glued to the same slab.
The technical evolution of production lines, more and more automated and fast, has given impulse to these reparation techniques, but the results are modest and partial.
Moreover such techniques are useful only for slabs which come out not fragmented from the blocks.
For many blocks the process doesn""t even start for the high risk of crumbling under the saw frame. In other cases the process starts but ends with a very low percentage of whole slabs.
The structural weakness of many raw stone materials is the reason why the stone activity has many difficulties to find industrial applications and continues in a hand-manufacturing way also in presence of a natural vocation for mass-production work.
An alternative technique that allows recovering raw material blocks of good decorative quality but with many structural defects, consists in impregnating the natural stone block with hardenable resins before starting the working cycle in factory.
Several attempts have already been done in this sense on parallelepiped blocks, driven from the logic that a process of impregnation in a vacuum state with resins able to shelter structural defects inside the block, would allow the resin to reach all structural defects which are in communication on the outside because of appearing of the defects on the surface of one of the six faces of the block.
But no one of these attempts allowed to reach acceptable technical-economic results, the consumption of resins necessary to the process is too elevated, the resins are in fact very expensive, and the same factories are expensive and difficult to manage.
Disregarding the treatment of the shapeless blocks, that is always disadvantageous, the treatment of parallelepiped square blocks requires heavy and expensive formworks that must be built around the block to form a tank that contains the block and the impregnation resin.
Since the quarry blocks don""t ever have the same dimensions, the problem of maintaining acceptable the consumption and the cost of the necessary impregnation resins remains without solution.
Some attempts have been made in order to use variable size formworks, but, besides the more elevated cost of the structure, the sealing between the walls forming the formwork was not guaranteed.
Italian Patent 1027222 described a method for forming a flexible container around a stone block, in particular a plastic bag, filling the spaces between the block so contained and the walls of a pressure tight container with an oil of specific weight. similar to the specific weight of the resins introduced inside the container.
Varying the level of the oil around the block, wrapped and protected from the plastic bag, it is possible to regulate the quantity of impregnation resin around the block.
Moreover it is provided that the oil is recovered after each operation in a reservoir external to the container to be subsequently reused in following impregnation operations.
This method nevertheless presents operational limits deriving from technical difficulties in the practical realization of the idea, beyond involving elevated management costs.
A first object of the present invention is therefore to make possible and practicable the impregnation of a whole quarry block with a vacuum impregnation process using hardenable adhesive resins.
These and other objects are reached from the impregnation method according to the present invention, as claimed in the accompanying claims.
The method according to the invention can be advantageously used for the consolidation of marble or stone blocks of various dimensions reducing the waste of resin and the total costs of treatment.